Explain what a pre-determined overhead absorption rate is and calculate six different overhead absorption rates using the given data.

$$\text{Rate} = \frac{\text{GH¢}72,000}{36,000 \text{ labour hours}} = \text{GH¢}2.00 \text{ per labour hour}$$

The overhead absorption rate per labour hour is $\boxed{\text{GH¢}2.00}$.

$$\text{Rate} = \frac{\text{GH¢}72,000}{\text{GH¢}108,000} \times 100\% = 66.67\%$$

The overhead absorption rate as a percentage of direct wages is $\boxed{66.67\%}$.

$$\text{Rate} = \frac{\text{GH¢}72,000}{\text{GH¢}48,000} \times 100\% = 150\%$$

The overhead absorption rate as a percentage of direct material cost is $\boxed{150\%}$.

$$\text{Rate} = \frac{\text{GH¢}72,000}{24,000 \text{ machine hours}} = \text{GH¢}3.00 \text{ per machine hour}$$

The overhead absorption rate per machine hour is $\boxed{\text{GH¢}3.00}$.

$$\text{Rate} = \frac{\text{GH¢}72,000}{16,000 \text{ units}} = \text{GH¢}4.50 \text{ per unit}$$

The overhead absorption rate per unit of production is $\boxed{\text{GH¢}4.50}$.

First, calculate the budgeted prime cost:

$$\text{Budgeted Prime Cost} = \text{Direct Material Cost} + \text{Direct Wages}$$ $$\text{Budgeted Prime Cost} = \text{GH¢}48,000 + \text{GH¢}108,000 = \text{GH¢}156,000$$

Now, calculate the rate:

$$\text{Rate} = \frac{\text{GH¢}72,000}{\text{GH¢}156,000} \times 100\% = 46.15\%$$

The overhead absorption rate as a percentage of prime cost is $\boxed{46.15\%}$.

$$\text{Prime Cost} = \text{Direct Material Cost} + \text{Direct Labour Cost}$$ $$\text{Prime Cost} = \text{GH¢}120 + \text{GH¢}270 = \text{GH¢}390$$

$$\text{Absorbed Overhead} = \text{Machine hours used} \times \text{Machine Hour Rate}$$ $$\text{Absorbed Overhead} = 60 \text{ hours} \times \text{GH¢}3.00/\text{hour} = \text{GH¢}180$$

$$\text{Total Cost} = \text{Prime Cost} + \text{Absorbed Overhead}$$ $$\text{Total Cost} = \text{GH¢}390 + \text{GH¢}180 = \text{GH¢}570$$

Let $SP$ be the Selling Price.

$$\text{Profit} = 20\% \text{ of } SP = 0.20 \times SP$$ $$\text{Total Cost} = SP - \text{Profit}$$ $$\text{GH¢}570 = SP - 0.20 \times SP$$ $$\text{GH¢}570 = 0.80 \times SP$$ $$SP = \frac{\text{GH¢}570}{0.80}$$ $$SP = \text{GH¢}712.50$$

The selling price to be charged for the batch order is $\boxed{\text{GH¢}712.50}$.