A cloud service is expected to be operational $24$ hours, Monday through Friday. Failures of the cloud service occur as follows:

Monday$=$ No failure

Tuesday$=5$ a$.$m$.$ to $7$ a$.$m$.$

Wednesday $=$ No failure

Thursday $=4$ p$.$m$.$ to $8$ p$.$m$.$

Friday $=8$ a$.$m$.$ to $11$ a$.$m$.$

The MTBF of this cloud service is