Solve the following problems: a) four 20ps - 74p = ? b) Convert 14 1/2 cm to mm

$$80 \text{p} - 74 \text{p} = 6 \text{p}$$

The result is $6 \text{p}$.

The final answer is $\boxed{6 \text{p}}$.

There are 10 millimeters in 1 centimeter.

$$14.5 \text{ cm} \times 10 \text{ mm/cm} = 145 \text{ mm}$$

The value is $145 \text{ mm}$.

The final answer is $\boxed{145 \text{ mm}}$.