Based on Pasewark and Riley$$s technique on evaluating beginning allowance for doubtful accounts to write$-$offs, what can be concluded from Figure $3?$

a$)$ Chevron has increasing write$-$off values

b$)$ Chevron has a consistent allowance for doubtful accounts and write$-$off relationship

c$)$ Verizon is overestimating its allowance for doubtful accounts

d$)$ Coca$-$Cola has an inconsistent allowance for doubtful accounts and write$-$off relationship