Researchers have determined that the amount of moisture present in a kernel of popcorn affects the volume of the popped corn and can be modeled for certain sizes of kernels by the function v(x) = -35.98 + 12.09x - 0.4450x², where x is moisture content (%, wet basis) and v(x) is the expansion volume (in cm³/gram). Describe the concavity of this function.