When {{MATH_29}} changes from {{MATH_30}} to {{MATH_31}}, {{MATH_32}} changes by {{MATH_33}} (rounded to the thousands place) given by {{MATH_34}} We can also estimate this change in {{MATH_35}} as {{MATH_36}} given by {{MATH_37}} We see that our approximation of the change in {{MATH_38}} is very close to the true change.