Different column widths with multicom

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The 5th row is killing me. How can i determine the width of the rows? I manage to scrap up the code underneath.

\begin{table}[h]    \centering    \begin{tabular}{|p{11.2cm}|p{3cm}|}    \hline       \textbf{Fag:}   & \textbf{Dato:} 17.01.20 \\    \hline        \multicolumn{2}{|l|}{\textbf{Prosjekt:}} \\    \hline        \textbf{Aktivitet:} & \textbf{Aktivitet nr: } \\    \hline        \multicolumn{2}{|l|}{\begin{tabular}[t]{p{7cm}|p{7cm}}         \textbf{Startdato:}  & \textbf{Sluttdato: }        \end{tabular}} \\     \hline    \end{tabular}\end{table}