$E_{r}^{i}$	Risk grade	RI value	Risk level	Risk degree
$E_{r}^{i} < 30$	Slight	RI < 40	A	Slight
$30 \leq E_{r}^{i} < 60$	Medium	40 ≤ RI < 80	B	Medium
$60 \leq E_{r}^{i} < 120$	Strong	80 ≤ RI < 160	C	Strong
$120 \leq E_{r}^{i} < 240$	Very strong	160 ≤ RI < 320	D	Very strong
$E_{r}^{i} \geq 240$	Extremely strong	RI ≥ 320	E	Extremely strong