How Ke is calculated

I was going through BPP exam kit Q 71.

They calculated Cost of Equity (Ke) as below;

Ziwa’s Co MV of debt 1785 M$ and MV of equity 1400M$.
Ziawa’s cost of capital is 9.4% and geared cost of equity is 16.83%. Pretax cost of debt is 4.76%. Tax rate 25%

The cost of equity is calculated as;

16.83%=Ke+.75(Ke-4.76%) x 1785/1400
Ke=10.93%

I am not understanding how this formula is derived or why they calculate in this way.

Kindly help.

Thanks.