Change to quotation calculation for website calculator

A the moment, we have a online calculator with one of the additional costs being 'Stamp Duty Land Tax'. At the moment the stamp duty tax works on the website based on the figure the customer enters. So for example, if £126,000 is entered, it calculates 1% of that number. The breakdown is as below: 0 – 125,000 = 0% 125,001 – 250,000 = 1% 250,001 – 500,000 = 3% Over 500,001 = 4% Stamp Duty Tax though has now changed and is more complex. - No stamp duty is paid for the first £125,000 of a property. - Then 2% will be paid on the proportion up to £250,000 (So if a property was £180,000, they would just pay 2% of £55,000). - Then 5% will be paid up to £925,000 (So if a property was £450,000, they would just pay 5% of £200,000). - Then 10% will be paid up to £1.5m (So if a property was £1m, they would just pay 10% of £75,000). - Then 12% will be paid over £1.5m (So if a property was £1.7m, they would just pay 10% of £75,000). A document attached also explains this change. I simply need the function code to be changed for this. Below is the code that is currently used for the simply calculation: public function getLandRegistryFee($purchaseamt = 0 ) { if( $purchaseamt) { if($purchaseamt > 0 and $purchaseamt <= 50000) { return 40; } else if($purchaseamt >= 50001 and $purchaseamt <= 80000) { return 70; } else if($purchaseamt >= 80001 and $purchaseamt <= 101000) { return 120; } else if($purchaseamt >= 101001 and $purchaseamt < 201000) { return 190; } else if($purchaseamt >= 201000 and $purchaseamt < 501000) { return 270; } else if($purchaseamt >= 501000){ return 540; } else{ return 0; } } else { return 0; } }