SAT Math Practice Question

The formula below is often used by project managers to compute $E$, the estimated time to complete a job, where $O$ is the shortest completion time, $P$ is the longest completion time, and $M$ is the most likely completion time.$$E=\frac{O+4 M+P}{6}$$Which of the following correctly gives $P$ in terms of $E, O$, and $M$ ?

1. A.$P=6 E-O-4 M$
2. B.$P=-6 E+O+4 M$
3. C.$P=\frac{O+4 M+E}{6}$
4. D.$P=\frac{O+4 M-E}{6}$