def calculate_rewards_common(covariates, coeffs_common):
    """Calculate common rewards.

    Covariates 9 and 10 are indicators for high school and college graduates.

    Parameters
    ----------
    covariates : np.ndarray
        Array with shape (num_states, 16) containing covariates.
    coeffs_common : np.ndarray
        Array with shape (2,) containing coefficients for high school and college
        graduates.

    Returns
    -------
    np.ndarray
        Array with shape (num_states, 1) containing common rewards. Reshaping is
        necessary to broadcast the array over rewards with shape (num_states, 4).

    Example
    -------
    >>> state_space = StateSpace(2, 1, [12, 16], 20)
    >>> coeffs_common = np.array([0.05, 0.6])
    >>> calculate_rewards_common(state_space.covariates, coeffs_common).reshape(-1)
    array([0.05, 0.05, 0.65, 0.65, 0.05, 0.05, 0.05, 0.05, 0.65, 0.65, 0.65,
           0.65])

    """
    return covariates[:, 9:11].dot(coeffs_common).reshape(-1, 1)