A stock is currently trading at $80.$ There are one$-$month calls and puts on the stock with strike prices of $70,75,80,85,$ and $90.$ The price and delta of each of these options is given below:

Strike: $70/75/80/85/90$

Call Price: $10\mathrm{.}60/6\mathrm{.}47/3\mathrm{.}39/1\mathrm{.}50/0\mathrm{.}56$

Put Price: $0\mathrm{.}30/1\mathrm{.}15/3\mathrm{.}05/6\mathrm{.}14/10\mathrm{.}18$

Call Delta $0\mathrm{.}92/0\mathrm{.}77/0\mathrm{.}54/0\mathrm{.}31/0\mathrm{.}14$

Put Delta: $-0\mathrm{.}08/-0\mathrm{.}23/-0\mathrm{.}46/-0\mathrm{.}69/-0\mathrm{.}86$

For each of the following portfolios:

$($a$)$ Long $100$ units of stock, short $100$ units of the $80-$strike call.

Find the current value of the portfolio

Find the approximate value of the portfolio following a $$1$ decrease in the stock price.

$($b$)$ Long $1000$ units of the $80-$strike call and $1174$ units of the $80-$strike put.

Find the current value of the portfolio

Find the approximate value of the portfolio following a $$1$ decrease in the stock price.