The pandemic years have been a very active time for Corporate Bonds, as many companies attempted to raise cash at record$-$low rates. For example, AT&T raised cash by selling a corporate bond in May $2020,$ with a time to maturity of $7$ years. They raised $2\mathrm{.}495$ billion USD, promising a face value of $2\mathrm{.}500$ billion USD, and a coupon rate of $2\mathrm{.}3\%$ per year, paid semiannually.

a$.$ What was the yield to maturity that investors required in May $2020?$

b$.$ Suppose a comparable U$.$S$.$ Treasury security showed a yield to maturity of $0\mathrm{.}53\%$ in May $2020.$ What was AT&T$$s credit spread?