Provide SML statement to achieve the following

You might use built$-$in functions such as hd$,$ tl$,$ floor, explode, etc.

val t $=(1,[[2],[3,5],[7]])$;

use :: nil style instead of $[]$ if you can

$(1)$ Form $4$ from t without using $1$

$(2)$ Form $[5\mathrm{.}0]$ from t

$(3)$ Form $[[7],$ nil, $[1]]$ from t without using $[]$

$(4)$ Form $[(1,2)]$ from t

$(5)$ Form $[$~$1\mathrm{.}5]$ from t