Final answer:
When string 2 breaks at t2=5n, the value of t1 is 0.
Step-by-step explanation:
In order to determine the value of t1, we need to understand the relationship between t1 and t2 when string 2 breaks. According to the given information, when t2=5n, string 2 breaks. This means that t1 must be equal to 0.