By selling an umbrella for ₹ 336, a shopkeeper loses 4%.

Let the CP of the umbrella be ₹ $x$.

SP of the umbrella = ₹336

Loss $=4 \%$ of $₹ x=₹ \frac{4}{100} x$

CP $-$ Loss $=$ SP

$\Rightarrow x-\frac{4}{100} x=336$

$\Rightarrow \frac{96}{100} x=336$

$\Rightarrow x=₹ 350$

$\therefore$ CP of the umbrella $=₹ 350$

Now, for gain of $4 \%$,

SP $=\mathrm{CP}+$ Gain

$\Rightarrow \mathrm{SP}=350+\frac{4}{100} \times 350$

$\Rightarrow \mathrm{SP}=350+14$

$\Rightarrow \mathrm{SP}=₹ 364$

Hence, in order to gain $4 \%$, the umbrella should be sold for ₹ 364 .