operating gearing

good evening

2 firms have the following cost structures:

Sales ——————- 5——–5
variable costs———(3)——-(1)
fixed costs ————(1)——-(3)
EBIT——————–1———-1

what is the level of operating gearing in each.

there are 3 ways to calculate op. gearing. and each gives a different answer. which one to use??

fixed costs/variable costs==================1/3=======3/1
fixed costs/total costs=====================1/4=======3/4

the answer is using fixed/total.

please explain

thank u