Answer
$180.9$ seconds
Work Step by Step
Water's specific heat is $4.186 \frac{kJ}{kg^{\circ}C}$. Therefore it takes, $150*17*4.186 = 10674.3 $ $kJ$ to heat the water up this much. For a $59 $ kW heater, this will take $10674.3/59$ seconds, or $180.9$ seconds.