calculating expected value

Hi again, back with another question! Here goes:

148 students ride in 4 buses, which transport 25, 33, 40 and 50 students respectively. A student is chosen at random. Let X be the number of student on the bus she's riding. Also, one of the 4 busdrivers are chosen at random. Let Y be the number of students on his bus.

Calculate expected values E[X] and E[Y].

(I've calculated expected value before but this question seems different and I'm really at a loss as to where to start.) Would really love some help with this!