Finding the efficiency of the water wheel

$($The following questions refer to the water wheel described in question $2.)$

a$)$ Suppose a mass of $0\mathrm{.}75kg$ of water in the bucket is raised to a height of $1\mathrm{.}5$ meters above the water wheel. How much gravitational potential energy does this water have relative to the water wheel? $($Show the math steps used to find your answer.$)$

b$)$ Suppose the plastic bottle with a mass of $0\mathrm{.}30kg$ is lifted to a height of $0\mathrm{.}45$ meters above the floor. How much gravitational potential energy does the bottle gain?

c$)$ Use your answers to parts a$)$ and b$)$ to find the efficiency of this process of water flowing from the bucket, turning the water wheel, and lifting the bottle.