1. Lets find the expenses she has to make -> 4*90+660=1020$(4 new tires + other expenses)
2. As her income is not set strictly we can guess the range she can save(More accurate calculations depends on her strict incomes). We have 5200-1020=4180$(if she gets paid 5200$) and 6250-1020= 5230$(if she gets paid 6250$).
3. So the range of savings vary from 4180 to 5230$$.
