Letter-number grid pattern completion

In the context of the given figure, which one of the following options correctly represents the entries in the blocks labelled (i), (ii), (iii), and (iv), respectively? Figure: a $4 \times 4$ grid with thick lines dividing it into four $2 \times 2$ blocks. Top-left block: N, U on top; 21, 14 below. Top-right block: F, (i) on top; 9, 6 below. Bottom-left block: H, L on top; 12, (iv) below. Bottom-right block: (ii), O on top; 15, (iii) below.