Julie drives \(100 \mathrm{mi}\) to Grandmother's house. On the way to Grandmother's, Julie drives half the distance at \(40 \mathrm{mph}\) and half the distance at \(60 \mathrm{mph}\). On her return trip, she drives half the time at \(40 \mathrm{mph}\) and half the time at \(60 \mathrm{mph}\).

a. How long does it take Julie to complete the trip to Grandmother's house?

b. How long does the return trip take?