modules/corporate.py

def calculate_wacc(equity: float, debt: float, cost_equity: float, cost_debt: float, tax_rate: float) -> float:
    """
    Calculates the Weighted Average Cost of Capital (WACC).
    equity, debt: market values
    cost_equity, cost_debt: decimal rates
    tax_rate: decimal tax rate (e.g., 0.21)
    """
    total_value = equity + debt
    if total_value == 0: return 0.0
    
    w_equity = equity / total_value
    w_debt = debt / total_value
    
    wacc = (w_equity * cost_equity) + (w_debt * cost_debt * (1 - tax_rate))
    return wacc

def calculate_capm(risk_free_rate: float, beta: float, market_return: float) -> float:
    """
    Calculates the expected return using the Capital Asset Pricing Model (CAPM).
    """
    return risk_free_rate + beta * (market_return - risk_free_rate)