WACC

**Followings are required**
- stock price
- num of issued shares (or avaliable shared in the market)
- debt
- tax
- earing before tax
- market premium rate

and using them
equity = stock price x num of issued shares
equity_cost = risk free rate + market premium rate
tax_rate = tax / earing before tax 

WACC formula:
https://en.wikipedia.org/wiki/Weighted_average_cost_of_capital