A nucleus of an element emits an alpha particle followed by a beta particle

A nucleus ₈₄X²⁰² of an element emits an alpha particle followed by a beta particle. The final nucleus is _aY^b. Find a and b.

Answer

₈₄X²⁰² → ₈₂Z¹⁹⁸ + ₂He⁴

₈₂Z¹⁹⁸ → ₈₃Y¹⁹⁸ + _-1β⁰

a = 83 and b = 198