Explain the special rules for offer and acceptance in regard to:

$2\mathrm{.}2\mathrm{.}1.$ Invitation to make an offer $(4)$

$2\mathrm{.}2\mathrm{.}2.$ Request for tenders $(4)$

$2\mathrm{.}2\mathrm{.}3.$ Silence $,($provide an example to support your answer$)$