We can use a simple equation to calculate the increase in gravitational potential energy.
PE = mgh
m is the mass of the object
g is the acceleration due to gravity
h is the change in height
PE = mgh
PE = (3.75 kg) (9.80 m/s^2) (1.5 m)
PE = 55.1 Joules
The increase in gravitational potential energy is 55.1 Joules.