Greenville Industries Uses the Accrual Basis to Account for All

Greenville Industries uses the accrual basis to account for all sales transactions. Sales for 2018 total $580,000. Included in this amount is $60,000 in receivables from sales on installment. Installment sales are considered revenue for book purposes, but not for tax purposes. Operating expenses total $100,000 and are treated the same for book and tax purposes. What is Greenville's book income?

A) $420,000
B) $480,000
C) $520,000
D) $580,000