After my quick research into how much a stone is... I got your target to be just under 10kg in about 3 months.
The answer is yes, you certainly can. Just remember that weight loss is a product of the net calorie intake... so while your exercise target is impressive, it will not guarantee any weight loss on its own. The diet makes up the other half.
So, eat reasonably and exercise regularly and you can certainly achieve your goal.
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