In parallelogram.

\( \Large d_{1}^{2} + d_{2}^{2}  = 2(l^{2} + b^{2})\)

\( \Large d^{2}+(10)^{2} \)=2(64+144)

=> \( \Large d^{2}=2\times 208-100 \)

=> \( \Large d^{2} \)=416-100=316

=> d=\( \Large \sqrt{316} \)

=> d=17.76 cm => d > 10