Use vector diagrams to predict the outcome of the sequence: 90(x) - - 90(x) when applied

Use vector diagrams to predict the outcome of the sequence:
90°(x) - τ - 90°(x)
when applied to equilibrium magnetization. In your answer, explain how the x-, y- and z magnetizations depend on the delay T and the offset Ω.
For a fixed delay, sketch a graph of the x- and y-magnetization as a function of the offset. At what values of QT do any nulls occur?