Answer:
Part a)


Part b)

Explanation:
Part a)
Constant speed by which the student will run is given as

now after some time if student is going to overtake the position of bus
so here the final positions will be same
so we have




so it is

So student will run the total distance



Part b)
Speed of bus when student reach the bus is given as



The answer is A ..........
Let the distance between the towns be d and the speed of the air be s.
distance = speed * time
convert the minutes time into hours.
When flying into the wind, ground speed will be air speed MINUS wind speed, hence the against the wind trip is described by:
d
s−15
=
7
3
return trip is then :
d
s+15
=
7
5
Cross-multiplying both we get the two-variable system:
3d=7∗(s−15)5d=7∗(s+15)
3d=7s−1055d=7s+105
subtract first equation from second equation we get
2d=210d=105km
Substitute the value of d in the above equations for s.
5∗105=7s+1057s=420s=60km/hr