Problem to be solved by visual basic

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hello!!
im just new in this field,im still studying as computer programmer in a Tesda school here in our town..

here's the problem,,i hope you can help me solve this tonight..

A car travelled 10 minutes in gravel,15 minutes in sand, 20 minutes in asphalt, 25 minutes in mud..
How can i run this,,that when i type for example 27 minutes so the car will be on the asphalt,,when i type the number of minute the corresponding place will appear in the textbox..

pls help me..pls..
thanks...(",)