S(x) = -x3 - 45x2 + 525x + 1429, 0 ≤ x ≤ 15 is an approximation to the number of salmon swimming upstream to spawn, where x represents the water temperature in degrees Celsius. Find the temperature that produces the maximum number of salmon.
◦ 5°C
◦ 12.5°C
◦ 10°C
◦ 0°C