A scientist, in his studies to model a person's blood pressure, uses a function of the type $P(t) = A + B\cos(kt)$ where $A$, $B$, and $K$ are positive real constants and $t$ represents the time variable, measured in seconds. Consider that a heartbeat represents the time interval between two successive maximum pressures.
When analyzing a specific case, the scientist obtained the data:
| Minimum pressure | 78 |
| Maximum pressure | 120 |
| Number of heartbeats per minute | 90 |
The function $P(t)$ obtained by this scientist when analyzing the specific case was
(A) $P(t) = 99 + 21\cos(3\pi t)$
(B) $P(t) = 78 + 42\cos(3\pi t)$
(C) $P(t) = 99 + 21\cos(2\pi t)$
(D) $P(t) = 99 + 21\cos(t)$
(E) $P(t) = 78 + 42\cos(t)$