Fig. P$6\mathrm{.}127$ and P$6\mathrm{.}128$

$6\mathrm{.}128$ The press shown is used to emboss a small seal at $E.$ Knowing that the vertical component of the force exerted on the seal must be $900$ N $,$ determine $($a$)$ the required vertical force $P,($b$)$ the corresponding reaction at $A.$