By definition, the Weighted Average Cost of Capital or WACC is the rate that an organization is expected to pay to all its security holders to finance its assets.
Mathematically this can be calculated by summation of the weighted average of the cost:
wacc = 0.4 * 0.06 + 0.15 * 0.075 + 0.45 * 0.13
wacc = 9.38%