Price an Option II

You have access to the European call options at the following strikes and $T_0$ prices, the underlying $S$ which has initial price $S_0 = 7$, and a bond that has initial price $0.9$, paying $1$ at time $T$. The calls are given in the format of $(\text{Strike } K, \text{Price } C_0)$

$$\begin{align*} (5, 4.2) \\ (10, 1.4) \\ (15, 0.7) \\ (20, 0.1) \end{align*}$$

Find the time-$0$ price of a contract that pays $\max({3S_T, 15})$ at time $T$.