Determine the total angle in a circle.

The total angle in a pie chart is $360^\circ$.

Given that $1^\circ$ represents Rs. 200.
Total monthly expenditure = Total angle $\times$ Value per degree
Total monthly expenditure = $360^\circ \times \text{Rs. } 200/\text{degree}$

The total monthly expenditure is Rs. 72,000.

The final answer for part (a) is $\boxed{\text{Rs. } 72,000}$.

Angle for Food = $18^\circ$.

Expenditure on Food = Angle for Food $\times$ Value per degree
Expenditure on Food = $18^\circ \times \text{Rs. } 200/\text{degree}$

The expenditure on Food is Rs. 3,600.

Angle for Hotel = $144^\circ$.

Expenditure on Hotel = Angle for Hotel $\times$ Value per degree
Expenditure on Hotel = $144^\circ \times \text{Rs. } 200/\text{degree}$

The expenditure on Hotel is Rs. 28,800.

To compare, we can find the difference between the two expenditures.
Difference = Expenditure on Hotel - Expenditure on Food

The expenditure on Hotel is Rs. 25,200 more than the expenditure on Food.

The final answer for part (b) is:
Expenditure on Food: $\boxed{\text{Rs. } 3,600}$
Expenditure on Hotel: $\boxed{\text{Rs. } 28,800}$
Comparison: The expenditure on Hotel is Rs. 25,200 more than on Food.