@Mohammadali Dastgheib
Here is the solution:

@Mohammadali Dastgheib
Just to clarify my question:

I am okay with R(t) values. It makes perfect sense.

I am okay with lambda values; it is the inverse of the MTBF values.

I just don't get how the MTBF values are calculated.

@Mohammadali Dastgheib
Mohammadali.pptx

Hello Mohammad, I have attached an example for your question that I had from one of the reliability seminars I took with Elsayed, hope you can open it.

basically 1- calculate the failure density function f(t)

2- Calculate Hazards rate h(t)

3- divide f(t)/h(t) to get R (reliability.

Note: when you calculate h(t) you have to remove previous failures from total survived units.

@Mohammadali Dastgheib

Background: see Kapur & Lamberson," Reliability in Engineering Design," Wiley, 1977
pages 13-35, and see examples like the on the right on pages 33-35.