I 'll be very grateful if you can help me , here is the question :
When a person sends an email, the probability that there is an attachment is 0.5. If there is an attachment then the size of the file is exponentially distributed with mean 5 kbytes. Let $X$ denote the size of the attachment received . Find the probability density function, distribution function of $X$ and $E[(X-2)^2]$.
Can you solve this question , i 'll try to understand it by your answers. There are some parts that i don't understand, and i think i can understand them by looking at the answers. Thank you so much.