Let's break down each transaction's impact on Preeya Naidoo's normal tax calculation:

$1.*$Loan from First National Bank $($R$50,000)$ for business equipment$*$

$-$ The loan itself isn't taxable income.

$-$ Interest paid on the loan $($R$4,500)$ is deductible as a business expense.

$2.*$Loan from Capitec $($R$6,500)$ for rental deposit on a townhouse$*$

$-$ The loan itself isn't taxable income.

$-$ Interest paid on the loan $($R$750)$ is not deductible as it's for a personal expense $($rental deposit$).$

$3.*$Dividends earned from a South African source $($R$4,000)*$

$-$ Dividends from South African companies are exempt from tax in the hands of the shareholder $($Preeya Naidoo$),$ as they're subject to Dividends Tax.

$4.*$Total revenue generated from the catering business $($R$550,000)*$

$-$ This revenue is taxable and will be included in Preeya's taxable income.

$5.*$SARS fine for late submission of provisional tax returns $($R$500)*$

$-$ The fine is not deductible for tax purposes, as it's a penalty.

In summary:

$-$ Business loan interest $($R$4,500)$ is deductible.

$-$ Personal loan interest $($R$750)$ is not deductible.

$-$ Dividends $($R$4,000)$ are exempt from tax.

$-$ Business revenue $($R$550,000)$ is taxable.

$-$ SARS fine $($R$500)$ is not deductible.

These transactions will impact Preeya's taxable income and normal tax calculation accordingly.