Solution :
We know,
![$\text{WACC}=\text{equity weightage } * \text{equity cost} + \text{net debt weightage} * \text{debt cost} * (1 -\text{tax rate})$](https://img.qammunity.org/2021/formulas/business/college/l0yr4un47swxq4259latnq7rvsl69bjjmh.png)
Net debt = debt market value - excess cash
= 110 - 10
= 100 million dollar
![$\text{net debt weightage}=\frac{\text{market value of net debt}}{\text{equity market value+ net debt market value}}$](https://img.qammunity.org/2021/formulas/business/college/abnz6zye4t8gdnhnh9eh652bcz4tb7hlca.png)
![$=(100)/(300+100)$](https://img.qammunity.org/2021/formulas/business/college/yxlwi072g3i4x3ivu6zd0drdnvupijw2lq.png)
= 0.25
![$\text{equity weightage}=\frac{\text{market value of equity}}{\text{equity market value+ net debt market value}}$](https://img.qammunity.org/2021/formulas/business/college/3rdpnmi0zhugzcq92ksmzcy2n4byxw6toa.png)
![$=(300)/(300+100)$](https://img.qammunity.org/2021/formulas/business/college/z9r4v9s9q1r91llkquuemnply4m9a2eyne.png)
= 0.75
Therefore, WACC = 0.75 x 12% + 0.25 x 5% x (1 - 31%)
= 0.75 x 12% + 0.25 x 5% x (1 - 0.31)
= 0.75 x 12% + 0.25 x 5% x 0.69
= 9% + 0.862%
= 9.862%