Wave height as a function of wind speed and duration

$($a$)$ What is the value of $\backslash ($ f$(30,20)\backslash )?$ What is its meaning?

According to the table, $\backslash ($ f$(30,20)=\backslash ),$ which means that if a $30$ knot wind has been blowing in the open sea for $20$ hours, it will create waves with estimated heights of $29$ feet.

$($b$)$ What is the meaning of the function of $\backslash ($ h$=$f$(20,$ t$)\backslash )?$ Describe the behavior of this function.

We fix $\backslash ($ v $\backslash )$ and $\backslash ($ t $\backslash ),$ resulting in a constant value.

$-$ We fix $\backslash ($ v$=20\backslash )$ and allow $\backslash ($ t $\backslash )$ to vary, resulting in an equation of one variable.

We fix $\backslash ($ t$=20\backslash )$ and allow $\backslash ($ v $\backslash )$ to vary, resulting in an equation of one variable.

We allow $\backslash ($ v $\backslash )$ and $\backslash ($ t $\backslash )$ to vary, resulting in a function of two variables.

$($c$)$ What is the meaning of the function $\backslash ($ h$=$f$($v$,20)\backslash )?$ Describe the behavior of this function.

We fix $\backslash ($ v $\backslash )$ and $\backslash ($ t $\backslash ),$ resulting in a constant value.

We fix $\backslash ($ v$=20\backslash )$ and allow $\backslash ($ t $\backslash )$ to vary, resulting in an equation of one variable.

We fix $\backslash ($ t$=20\backslash )$ and allow $\backslash ($ v $\backslash )$ to vary, resulting in an equation of one variable.

We allow $\backslash ($ v $\backslash )$ and $\backslash ($ t $\backslash )$ to vary, resulting in a function of two variables.