How to memorize everything faster

One who eats everything

A student studying a foreign language has 50 verbs to meemorize, the rate at which the student can memorize these verbs is proportional to the number of verbs remaining to be memorized, that is, if the student memorizes y verbs in t minutes, dy/dt=k(50-y) Assume that initially no verbs are memorized, and suppose that 20 verbs are memorized in the first minutes. How many verbs will the student memorize in t min.