In an isosceles \bigtriangleup ABC, AB = AC and \angle B = 4 \angle A. Find the angles of the triangle.

Question

( A ) 20^{\circ},70^{\circ},80^{\circ}
( B ) 40^{\circ},40^{\circ},100^{\circ}
( C ) 30^{\circ},70^{\circ},80^{\circ}
( D ) 20^{\circ},80^{\circ},80^{\circ}