17.31 USE problems

Problem: Find all values of the parameter \( a \), for each one of which the equation \( \left|\xi^{2}-49\right|-12|\xi-a|- \) \( -12 a=0 \) with respect to the variable \( \xi \) has exactly 4 solutions. If the question of the task allows several variants of answer, show them in the form of a set.