Question $3(3$ marks$)$: How long would it take to heat the water in a $60-$gallon electric water heater from $40$ to $150F$ if the heating element delivers $7kW?$ Assume all of the electrical energy is converted to heat in the water, neglect the energy required to raise the temperature of the tank itself, and neglect any heat losses from the tank to the environment.

$($Hint: Change in internal energy $=mcT,$ Power is the rate of doing work so it has units of energy per unit of time, Water density $=8\mathrm{.}34I\frac{b}{g}al,1W=3\mathrm{.}4121Bt\frac{u}{h}r$