Based on data from the U.S. Census Bureau, an approximate family income distribution for the U.S. is given by the function ƒ(x) = 0.00462x³ - 0.160x² + 1.30x + 2.85, where ƒ(x) is the number of families (in millions) and x is the annual income in units of $10,000, with 0 ≤ x ≤ 20. For example, x = 7.5 represents an annual family income of $75,000. This function does not give a good representation for family incomes over $200,000. The number of families (in millions) with an income in a given range can be found by integrating this function over that range. Find the number of families with an income between $50,000 and $75,000.