jelaskan formula perfect tense and past perfect tense?

Past Perfect Tense : S + had + Past Participle (PP.) of the Verb + O
Example = She had written a letter

Perfect Tense -nya yang mana ??
Past Perfect Continuous Tense : S + had been + V + ing + O + since/for
Example : We had been writing a letter since morning

Present Perfect Tense : S + has/have + Past Participle (PP.) of the Verb + O
Example = They have written a letter

kalau perfect tense: rumus untuk
kalimat verbal i/we/you/they+have+past participle
he/she/it+has + past participle