Dear Mr/Mrs. ...
I have seen your job offer posted on the local newspaper and I am extremely interested in this type of voluntary work which is done/promoted by your centre. Fortunately, I have already had past experiecce in taking care of handicapped children as I used to take part in one of the similar activities organized by my school, so I can confidently claim that I am capable of handling this work. Moreover, I find it interesting and eye-opening while doing such voluntary work as I have a chance to devote my time and effort to helping other unfortunate people. I would appreciate the opportunity for explaining how I feel I am suit for this position you are offering.
I am available for interviews at any time which is convenient to you. You can contact me via email address given.
I am looking forward to hearing from you.
Yours faithfully,
....
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