A wooden board is shaped liked a rectangular prism. It has a total volume of 324 cubic inches. The width is 3 inches less than the height and the length is 12 inches longer than the height. What are the dimensions of the board?

Write a polynomial function f of least degree that has rational coefficients, a leading coefficient of 1, and the given zeros. 3, 4+2i, 1+(sqrt)7 the answer is supposed to be: f(x)=x(^5)-13x(^4)+60x(^3)-82x(^2)-144x+360 what am i doing wrong?