How to solve this question?

Richard's preferences over chocolate, c, and money, m, can be represented by the utility function:

u(c, m) = 6c + m + 6 (c r_c) + (m r_m)

where r_c is his chocolate reference point, r_m is his money reference point, and the function is defined as:

(x) = x when x >= 0

(x) = 1.5x when x < 0

If his reference point is the status quo (that is, his initial endowment), what is the maximum price Richard would be willing to pay to buy a chocolate?