Final answer:
The net book value of the patent on the balance sheet at December 31, 2015, considering the change in its estimated useful life, would be $652,800. This figure includes initial amortization for three years and the revised amortization for 2015 after adjusting the useful life to 10 years.
Step-by-step explanation:
When Hess Co. purchased the patent for $952,000 with an initial life of 15 years, annual amortization would be calculated as $952,000 / 15 years = $63,466.67. By 2015, three years of amortization have already been recorded, so the accumulated amortization at the start of the year would be $63,466.67 x 3 = $190,400. When Hess Co. revised the useful life to 10 years in 2015, the remaining cost to be amortized over the remaining 7 years would be $952,000 - $190,400 = $761,600. The new annual amortization expense would then be $761,600 / 7 = $108,800. Since the revision was made in 2015, for that year alone, we would record this revised expense. Therefore, the accumulated amortization at the end of 2015 would be $190,400 (initial three years) + $108,800 (for 2015) = $299,200. Consequently, the patent's net book value on December 31, 2015, would be the initial cost of $952,000 less the accumulated amortization of $299,200, resulting in $652,800.