1. The problem statement, all variables and given/known data 2. Relevant equations It = I∞ (1-2 exp -τ/T1) Or I've got T1 = τn/ln2 where τn is the τ at node (M = 0) 3. The attempt at a solution So would I plot τ vs amplitude on a graph and then what? Everything I've found seems to use a programme to do it?