Two externally tangent circles on a baseline

Two circles rest on the same horizontal line and touch externally. The larger centre is \(O\), radius \(15\) cm; the smaller centre is \(C\), radius \(x\) cm. The horizontal through \(O\) meets the vertical through \(C\) at \(B\), and \(B\) lies on the larger circle. Let vertical feet be \(E,F\).

1. Express
   1. \(OC\),
   2. \(BC\), in terms of \(x\).
2. Find \(x\).
3. Find area of trapezium \(OCEF\).