a different cross-country time question

Suppose that I fly from airport "a" to airport "b" and then from
airport "b" to airport "c". The straight-line distance from "a" to
"b" is less than 50 nautical miles and the straight-line distance from
"b" to "c" is less than nautical miles. However, the straight-line
distance from "a" to "c" is more than 50 nautical miles. How much
time can I spend at airport "b" and still count this flying as
cross-country time for the purpose of meeting the aeronautical
experience requirements for an instrument rating?

Thank-you!
Arden