"I gave 40 hours"
Depends on what the system is doing ... Drawing Pictures for the list of actions or event steps the Actor will do to achieve a goal.
Simple ... a Few Minutes:
Register at school for a class .....
Register For a Class
Complex Car Rental ... Maybe a Day or More .....
Search For Nearest Rental Center
Search For Car
Reserve Car For a Date and Time
Select Options - GPS, Satellite Radio, etc.
Pay For Car
Will Customer Pick Up Car Or Be Delivered To Them
Send Receipt To Renter
And ... Is That 40 Hours You Gave Considered a Work Week or Project Time ?
Many of the projects I've been on use about 85% Working Project time during the day ... you have meetings, phone calls, lunch, BSing with friends, maybe a broken computer, etc. that will take away from your actual project work time.
So, the actual 40 hours you specified could actually be 1 whole week plus some of the following week to get 40 hours ... then the managers want to know why you are behind schedule ...
Or you say 40 hours and they finish in 1 day and start goofing off ... then the managers want to know why your estimation is way off ... so, be clear.
Be careful estimating hours ... I'll usually go to the person or team going to do the work, let them see what has to be done, get an estimate from them and then add some buffer-space ... hand it to your manager with a smile ... be prepared to get questioned and be told to do it in less time and money.
And remember ... keep your resume updated.