Answer:
a
b

Explanation:
From the question we are told that
The distance travel in 4.22 s is
The mass of the cart plus the fan is
Generally from kinematic equation we have that

Here u is the initial velocity with value 
So
=> 
Generally the net force is

=>
=>
Gnerally the new mass of the cart plus the fan is
The distance considered is 
Generally the new acceleration of the cart is mathematically represented as

=> 
=> 
=> 
Gnerally from kinematic equation we have

Here u is the initial velocity and the value is zero because it started from rest
=> 
=> 