What is the answer . What is the formula to calculate it

Dear Student,
Answer hereunder provided by taking the assumption, considering National GDP as Nominal GDP.

$$\begin{gathered} Real GDP =\frac{Nominal GDP}{Price Index of Current Year} \times 100 \\ Substituting the values in the formula :- \\ 200=\frac{200}{Price Index of Current Year} \times 100 \\ Price Index of Current Year = \mathbf{100}\mathbf{ }\mathit{A}\mathit{n}\mathit{s}\mathit{w}\mathit{e}\mathit{r} \end{gathered}$$

Regards