5 Use Parseval's identity to compute the following integrals. \text { a) } \int_{-\infty}^{\infty} \operatorname{sinc}^{2}(2 r) d t \text {, } \text { (b) } \int_{0}^{\infty} \operatorname{sinc}(t) \operatorname{sinc}(2 t) d

t \text {. }