The mirror formula for curved mirrors is:

where
f is the focal length of the mirror

is the distance of the object from the mirror

is the distance of the image from the mirror
The sign convention that should be used in order to find the correct values is the following:
-

: positive if the mirror is concave, negative if the mirror is convex
-

: positive if the image is real (located on the same side of the object), negative if it is virtual (located on the opposite side of the mirror)
$0.60
90 mins is 1.5 hrs
5 kW × 1.5 = 7.5 kWh
7.5 kWh × $0.08 = $0.60
I attached my work and highlighted my answers. Hope it makes sense! please comment back with any questions if anything is still unclear! :)
Answer:
d
Explanation:
This is because momentum is defined as p = mv
delta p = Force *time
neither velocity nor time is given so a conclusion cannot be made on which has the greatest momentum change.