At 1/2 full-load, the load losses (I^2*R) is 1910W
Now, find the load losses at full-load. If R is constant and I goes up by two, then (I^2) * R will go up by (2^2) or 4.
At full-load, the load losses are 4*1910W = 7640W
Total Loss = Core Loss + Load Loss = 460W + 7640W = 8100W