Price an Option I

You have access to European call options at the following strikes and $T_0$ prices, as well as the underlying $S$ with an initial price of $S_0 = 21$. The calls are given in the format of $(\text{Strike } K, \text{Price } C_0)$

$$\begin{align*} (15, 4.2) \\ (20, 1.4) \\ (25, 0.7) \\ (30, 0.1) \end{align*}$$

Find the time-$0$ price of a contract that pays $\min({S_T, 25})$ at time $T$.